- Bipolar disorder is a common mood disorder that affects 1% to 2% of the population. Individuals with bipolar disorder tend to have periods of mania that are characterized by extra energy, very poor judgment or unrealistic beliefs about their thoughts and abilities, and an inability to complete thoughts and tasks; as well as major depressive episodes. The range and frequency of symptoms in affected individuals can vary greatly. Most individuals have cyclical symptoms and spend more time in a normal mood state than in an overtly symptomatic state.